Wireless communications system and method

ABSTRACT

A wireless communications system includes a base station, a plurality of intermediate devices, and a terminal device. Downlink communications may be provided directly from the base station to the terminal device, including control signals which instruct the terminal device where to send uplink data. This enables the base station to directly control scheduling of uplink communications, and in particular to define an uplink route from the terminal device to the base station via one or more intermediate devices. Power is conserved at the terminal device on the uplink because a lower power transmission can be used which although insufficient to reach the base station can reach the intermediate device. The terminal device is not required to determine the uplink path itself and therefore does not require complex, expensive, and power consuming control logic.

FIELD OF THE INVENTION

The present invention relates to a wireless communications system andmethod. Further aspects of the present invention relate to a basestation, an intermediate device, a terminal device and a computerprogram.

BACKGROUND OF THE INVENTION

Machine Type Communication (MTC) is being discussed in various wirelesscommunication standards bodies as a new trend of wireless technology ofcommunication network applications which typically do not require humaninteraction.

A broad definition of MTC is an automated communication network to andfrom machines. One major category of MTC devices are expected to havethe characteristics of very low power consumption, very small datatransmissions and a very large number of terminals. An example MTCapplication that fits within this category may for example be energyconsumption monitoring of home appliances for smart grid systems.

In order to realize these requirements, wireless PAN (Personal AreaNetwork: 10-20 m range) standards such as ZigBee adopt Adhoc/Meshtopology where there is no central coordinating entity to control thetraffic flow, and where the scheduling/routing of data transmission ismanaged in a distributed manner. The Mesh characteristics allow data tobe conveyed beyond the PAN range by multihopping the information via aseries of neighbouring devices. Because each transmission link is keptshort, the power consumption per terminal is kept low.

However, in order to reliably convey information from a source to adestination, this topology encounters several problems.

Routing/Scheduling Complexity

One characteristic of Mesh topology is that there could be multipleroutes from source to destination. FIG. 1 schematically illustrates aMesh network topology. Seven terminal devices A to G are shown. In orderto transfer information from terminal A to terminal G, route 1 (solidarrows) or route 2 (dashed arrows) can be taken. The arrows accompaniedby question marks indicate alternative routes available for transmissionfrom a given terminal. In particular, terminal A needs to make adecision whether to transmit its data first to terminal B (via solidarrow), or to terminal C (via dashed arrow). Terminal D needs to make asimilar decision. This means that each terminal in a Mesh topologyrequires knowledge of the existing surrounding terminals and requiresthe capability to select the optimum route to a given destination, whichintuitively requires significant intelligence.

Furthermore, in an energy conserving system, some terminals may berequired to switch into a hibernation mode when they are not required toreceive or transmit. In such a scenario, because there is no centralcoordinator, each terminal is required to have knowledge of when theneighbouring terminals are capable to receive information, which wouldimpact on how they schedule transmission.

Hidden Node Problem

As described above, in a Mesh topology each terminal is required to makea decision on when to transmit data. FIG. 2 schematically illustrateshow this can be problematic due to hidden nodes. In FIG. 2, fourterminals A to D are shown, with the radio transmission range ofterminals A and C being indicated by the circles surrounding theserespective terminals. In the deployment scenario envisaged in FIG. 2,where terminal A has data to send to terminal B, and terminal C has datato send to terminal D, because terminal A is not in range of C and viceversa, there is possibility that terminals A and C may commencetransmission at the same time. In this situation, a mixed signal fromterminals A and C will be received at terminal B, which may inhibitdecoding of the desired signal (from terminal A) at terminal B. A“listen before send” mechanism at the transmitting terminals (toobserver for interfering transmissions) will not work in this casebecause the transmitting terminals are out of range of each other, or inother words are hidden from each other. Complex mechanisms would berequired to effectively solve this hidden node problem.

Excessive Use of Resource (Medium & Energy)

The nature of the Mesh topology requires the same data to be transmittedmultiple times through multiple hops. FIGS. 3A and 3B schematicallyillustrate how control signals are communicated from a terminal A to aterminal G, and how in response data signals are communicated from theterminal G to the terminal A. In particular, FIG. 3A illustrates asingle hop scenario whereas FIG. 3B illustrates a multi-hop scenario. InFIG. 3A, the terminals A and G communicate directly with each other.Neighbouring (intermediate) terminals B, D and E are not utilised in thecommunication. More specifically, the terminal A sends a control signaldirectly to the terminal G to request data, and the terminal Gresponsively transmits the requested data directly back to the terminalA. The period between the transmission of the control signal from theterminal A to the reception of the data at the terminal A is referred toas the transmission time. In contrast, in FIG. 3B, the terminals A and Gcommunicate with each other via the terminals B, D and E, in a multi-hopmanner. More specifically, the terminal A sends a control signal torequest data firstly to the terminal B. Terminal B then relays thecontrol signal to the terminal D, and so on through the terminal E untilthe control signal is finally received at the terminal G from theterminal E. The terminal G then responsively transmits the requesteddata firstly to the terminal E, where it is relayed on to the terminal Dand so on through the terminal B until the data is finally received atthe terminal A. As with FIG. 3A, the period between the transmission ofthe control signal from the terminal A to the reception of the data atthe terminal A is referred to as the transmission time.

As can be understood from a comparison of FIGS. 3A and 3B, not only doesmulti-hopping increase the latency to transfer information from sourceto destination, but it also has some additional side effects. One effectis, since the same data needs to be sent multiple times, it consumesmore medium time than when transmitted in a single hop. Routing signalsand traffic flow control signals may also be sent multiple times, makingthe effect more serious. This problem is particularly significant in MTCwhere there may be large numbers of terminals, and for which thesignalling information (control signals) is likely to dominate theactual information (data) transmitted.

Also, because in a Mesh topology terminals within the route (terminalsB, D & E in FIG. 3B) need to receive and transmit data and signallingthat is not originated by itself, they are required to consume moreenergy than in a single hop network, in which they would only transmitself-originated data. These same problems (excessive use of medium) canbe observed in a Relay topology or when a gateway is used.

Accordingly, it will be understood that one of the main characteristicsof MTC is that terminals are expected to have extremely low powerconsumption. One effective way to realize this is to limit thetransmission range of the MTC terminals, and to use Relay or Meshtopology to multihop the information from the MTC terminals to the basestation.

However, it will also be understood from the above discussion that Relayand Mesh topologies have their own drawbacks in that each relay or meshterminal needs to have distributed scheduling and routing capability inorder to convey information in a multihop manner, which bringscomplexity to these terminals. Furthermore, the scheduling messages needalso to be multihopped, which results in an ineffective use of themedium.

An uplink only single-hop relay is described in US2008/0285499. Themobile terminal in this case is agnostic to the relay node, that is itis not aware that its uplink data is being forwarded by the relay node.One characteristic of this transparent operation is that the relay nodeonly transmits towards the base station (eNB), and never to the mobileterminal (UE). This creates some problems. For example, this arrangementwill not work with a Type 1 relay of the sort that is being standardizedin 3GPP. Additionally, there is no way to enforce per link automaticrepeat requests (ARQ). There is no way to compensate for additionaluplink delay caused by two or more hops. Also, there is no way tomeasure downlink channel quality between individual multihop links.

SUMMARY OF THE INVENTION

According to the present invention there is provided a wirelesscommunications system comprising:

a base station;

a plurality of intermediate devices; and

a terminal device; wherein

the base station is operable to wirelessly transmit downlink signals tothe terminal device, the downlink signals comprising terminal controlsignals identifying one of the intermediate devices as a target deviceto which the terminal device is to direct uplink signals intended forthe base station; and

the terminal device is operable to wirelessly transmit the uplinksignals to the base station via the intermediate device identified bythe terminal control signals.

In this way, downlink communications are provided directly from the basestation to the terminal device, including control signals which instructthe terminal device where to send uplink data. This enables the basestation to directly control scheduling of uplink communications, and inparticular to define the uplink route from the terminal device to thebase station via one or more intermediate devices. Preferably, the basestation is operable to wirelessly transmit the downlink signals directlyto the terminal device. There is no problem with the base stationcommunicating directly with the terminal device on the downlink, becausethere is no requirement to conserve power at the base station. Power isconserved at the terminal device on the uplink because a lower powertransmission can be used which although insufficient to reach the basestation is able to reach the intermediate device. The terminal device isnot required to determine the uplink path itself and therefore does notrequire complex, expensive and power consuming control logic.

In other words, in order to mitigate the conflicting requirements setout in the above background, a method to use a Relay and/or Meshtopology for uplink transmission to conserve power at MTC terminals,while using conventional Star topology in the downlink transmissionwhere there is sufficient transmission power at the base station isproposed.

The base station may be operable to wirelessly transmit intermediatecontrol signals to an intermediate device via which the uplink signalsare to be routed, the intermediate control signals indicating eitheranother of the intermediate devices or the base station as a targetdevice to which that intermediate device is to direct the uplinksignals. In this case, the intermediate device is operable to wirelesslytransmit the uplink signals to the intermediate device or base stationidentified by the intermediate control signals. In this way, the basestation directly selects all of the radio links in the chain between theterminal device and the base station.

The base station may be operable to wirelessly transmit to theintermediate device an indication that it is required to receive theuplink signals. This indication may specify a radio resource at whichthe intermediate device can expect the uplink signals to be transmittedto the intermediate device by the terminal device or by anotherintermediate device. This may allow the receiving intermediate device toswitch into a “relaying” mode (from a dormant mode for example) and todecode information from the correct radio resources.

When the uplink signals are to be routed via more than one intermediatedevice, the base station may be operable to wirelessly transmitintermediate control signals to a first intermediate device via whichthe uplink signals are to be routed, the intermediate control signalsindicating a second intermediate device as a target device to which thefirst intermediate device is to direct the uplink signals. In this case,the first intermediate device is operable to wirelessly transmit theuplink signals to the second intermediate device identified by theintermediate control signals.

The terminal control signals may comprise scheduling information havingmore than one address field, the address fields comprising a transmitteraddress field identifying the terminal device and a receiver addressfield identifying the intermediate device via which the uplink signalsare to be transmitted. The intermediate control signals may alsocomprise scheduling information having more than one address field, theaddress fields comprising a transmitter address field identifying thefirst intermediate device and a receiver address field identifying thesecond intermediate device. The address fields may be radio networktemporary identifiers (RNTIs) specified on a physical downlink controlchannel (PDCCH) broadcast by the base station. It may not be necessaryto provide two address fields in the scheduling information to theintermediate device from which the base station is to directly receiveuplink signals. This is because it may be considered implicit that inthe absence of the second address the uplink data is to be transmittedto the base station providing the scheduling information.

The intermediate devices may be operable to generate respectivepredetermined beacon signals. The terminal device may then receive abeacon signal from an intermediate device and generate a respectivemeasure of the radio link quality between the terminal device and theintermediate device using the received beacon signal. The terminaldevice then transmits the measure of radio link quality to the basestation within the uplink signals. The terminal device may receive thebeacon signals from plural intermediate devices and generate, for eachradio link between the terminal device and one of the intermediatedevices from which a beacon signal has been received, a respectivemeasure of the radio link quality using the received beacon signals.Again, the terminal device may then transmit the respective measures ofradio link quality to the base station within the uplink signals. Thebase station may then determine a transmission route from the terminaldevice to the base station via one or more of the intermediate devicesin dependence on the received measures of radio link quality.

One or more of the base station, the intermediate devices and theterminal device may be operable to generate respective predeterminedbeacon signals. Another one or more of the base station, theintermediate devices and the terminal device receive the beacon signalsand generates a respective measure of the radio link qualitycorresponding to the radio link via which the beacon signal has beentransmitted using the received beacon signals. The another one or moreof the base station, the intermediate devices and the terminal devicemay then transmit the measure of radio link quality to the base stationwithin the uplink signals, whereupon the base station is able todetermine a transmission route from the terminal device to the basestation via one or more of the intermediate devices in dependence on themeasures of radio link quality.

In this way, the various devices within the network are able to discoverneighbouring devices and the quality of radio links with thoseneighbouring devices. The base station is able to receive all of thisinformation to determine a suitable route through the network for uplinkdata. It will be appreciated that it may not be necessary for alldevices to transmit beacon signals, particularly where certain radiolinks are fixed geographically.

The control signals may comprise scheduling information, the schedulinginformation specifying one or more of a transmission power, data rate,transmission frequency, transmission timeslot and number of resourceblocks for the uplink signals. The scheduling information may be set bythe base station for each radio link based on the radio link qualitymeasure reported for each radio link.

The base station may broadcast an indication of the radio resource overwhich each beacon signal is transmitted.

The uplink signals from the terminal device may comprise uplink controlsignals indicating a radio link quality between the terminal device andneighbouring devices. The base station may then set one or more of anuplink route from the terminal device to the base station via one ormore of the intermediate devices and transmission control parameters forcontrolling the transmission of data from each device in the uplinkroute in dependence on the received uplink control signals.

In one embodiment, the intermediate devices generate respectivepredetermined beacon signals. The terminal device receives a beaconsignal from an intermediate device and generates a respective measure ofthe radio link quality between the terminal device and the intermediatedevice using the received beacon signals. The terminal device thentransmits the measure of radio link quality to the intermediate device.The intermediate device may then relay the measure of radio link qualityto the base station.

In an embodiment, in response to receiving uplink data signals from theterminal device via one or more intermediate devices, the base stationis configured to transmit a first acknowledgement message to theintermediate device from which the uplink signals have been directlyreceived, and to transmit a second acknowledgement message directly tothe terminal device. The intermediate device from which the uplinksignals have been directly received retains the uplink signals until thefirst acknowledgement message has been received at the intermediatedevice, and the terminal device retains the uplink signals until thesecond acknowledgement message has been received at the terminal device.

The base station may determine a delay budget for uplink datatransmission based on the number of intermediate devices via whichuplink data transmissions from the terminal device to the base stationare to be routed. The base station can use the determined delay budgetto set a time-out period after which an uplink signal transmitted fromthe terminal device to the base station can be assumed to be lost.

The intermediate devices may be dedicated relays, other terminal devicesor a combination of the two (that is, some of the intermediate devicesmay be dedicated relays while other of the intermediate devices may beterminal devices). The terminal device transmitting uplink signals tothe base station may in some embodiments serve as an intermediate devicein relation to uplink communications from another terminal device to thebase station.

The terminal devices may be machine type communication (MTC) devices.The downlink signals may comprise data signals.

According to another aspect of the present invention, there is provideda base station for wirelessly communicating data to and from a terminaldevice via one or more of a plurality of intermediate devices within awireless communications system, the base station comprising:

a transmitter configured to wirelessly transmit downlink signals to theterminal device, the downlink signals comprising control signalsindicating one of the intermediate devices as a target device to whichthe terminal device is to direct uplink signals intended for the basestation; and

a receiver configured to receive uplink signals transmitted from theterminal device via the intermediate device indicated by the controlsignals.

According to another aspect of the present invention, there is provideda terminal device for wirelessly communicating data to and from a basestation via one or more of a plurality of intermediate devices within awireless communications system, the terminal device comprising:

a receiver configured to wirelessly receive, from the base station,downlink signals, the downlink signals comprising terminal controlsignals indicating one of the intermediate devices as a target device towhich the terminal device is to direct uplink signals intended for thebase station; and

a transmitter configured to wirelessly transmit the uplink signals tothe base station via the intermediate device indicated by the terminalcontrol signals.

According to another aspect of the present invention, there is providedan intermediate device for wirelessly relaying data between a basestation and a terminal device within a wireless communications system,the intermediate device comprising:

a receiver configured

to wirelessly receive, from the base station, intermediate controlsignals indicating another intermediate device or a base station as atarget device to which the intermediate device is to direct uplinksignals intended for the base station; and

to wirelessly receive, from the terminal device or from anotherintermediate device, the uplink signals intended for the base station;and

a transmitter configured to wirelessly transmit the received uplinksignals to the intermediate device or the base station indicated by theterminal control signals.

According to another aspect of the present invention, there is provideda method of wirelessly communicating data between a base station and aterminal device via one or more of a plurality of intermediate devices,comprising:

wirelessly transmitting, from the base station, downlink signals to theterminal device, the downlink signals comprising terminal controlsignals indicating one of the intermediate devices as a target device towhich the terminal device is to direct uplink signals intended for thebase station; and

wirelessly transmitting, from the terminal device, the uplink signals tothe base station via the intermediate device indicated by the terminalcontrol signals.

According to another aspect of the present invention, there is provideda method of wirelessly communicating data between a base station and aterminal device via one or more of a plurality of intermediate deviceswithin a wireless communications system, comprising:

wirelessly transmitting downlink signals from the base station to theterminal device, the downlink signals comprising terminal controlsignals indicating one of the intermediate devices as a target device towhich the terminal device is to direct uplink signals intended for thebase station; and

receiving, at the terminal device, uplink signals transmitted from theterminal device via the intermediate device indicated by the terminalcontrol signals.

According to another aspect of the present invention, there is provideda method of wirelessly communicating data between a terminal device anda base station via one or more of a plurality of intermediate deviceswithin a wireless communications system, comprising:

wirelessly receiving at the terminal device, from the base station,downlink signals, the downlink signals comprising terminal controlsignals indicating one of the intermediate devices as a target device towhich the terminal device is to direct uplink signals intended for thebase station; and

wirelessly transmitting the uplink signals from the terminal device tothe base station via the intermediate device indicated by the terminalcontrol signals.

According to another aspect of the present invention, there is provideda method of wirelessly relaying data between a base station and aterminal device within a wireless communications system, comprising:

wirelessly receiving at an intermediate device, from the base station,intermediate control signals indicating another intermediate device orthe base station as a target device to which the intermediate device isto direct uplink signals intended for the base station;

wirelessly receiving at the intermediate device, from the terminaldevice or from another intermediate device, the uplink signals intendedfor the base station; and

wirelessly transmitting the received uplink signals to the intermediatedevice or the base station indicated by the intermediate controlsignals.

A computer program and a recording medium for implementing the inventionare also envisaged.

According to yet another aspect of the present invention there isprovided a wireless communications system comprising:

a base station; and

a plurality of terminal devices; wherein

the base station is operable to wirelessly transmit downlink signalsdirectly to a first one of the terminal devices; and

the first terminal device is operable to wirelessly transmit the uplinksignals to the base station via a second one of the terminal devices.

In this way, an asymmetric uplink/downlink mesh network can be provided.A corresponding base station, terminal device and method are alsoenvisaged.

Further aspects and features of the present invention are defined in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments of the present invention will now be described withreference to the accompanying drawings in which like parts have the samedesignated references and in which:

FIG. 1 schematically illustrates a mesh network having multiple possibletransmission routes;

FIG. 2 schematically illustrates a “hidden node” problem in a meshnetwork;

FIGS. 3A and 3B provide a comparison of resource consumption in singlehop and multi-hop transmissions;

FIGS. 4A and 4B provide a comparison between a symmetric uplink/downlinkmulti-hop signalling scenario and an asymmetric uplink/downlinksignalling scenario;

FIGS. 5A and 5B provide a comparison of resource consumption for the twoscenarios shown in FIGS. 4A and 4B respectively;

FIGS. 6A and 6B provide a comparison of the symmetric uplink/downlinkmulti-hop signalling scenario and the asymmetric uplink/downlinksignalling scenario when applied to a relay network;

FIG. 7 is a schematic block diagram of a mobile communications networkand mobile communications devices forming a communication system whichoperates in accordance with the 3GPP Long Term Evolution (LTE) standard;

FIG. 8 schematically illustrates an example downlink data and controlchannel structure for use in the network shown in FIG. 7;

FIG. 9 schematically illustrates an example uplink data and controlchannel structure for use in the network shown in FIG. 7;

FIG. 10 schematically illustrates an example signal flow fortransmitting and receiving beacon signals, and allocating uplinkresources in dependence on the result;

FIG. 11 schematically illustrates the use of the downlink control anddata channels to control the transmission of beacon signals from variousdevices on the network;

FIG. 12 schematically illustrates an example signal flow for setting anuplink data transfer route and providing uplink data in response;

FIG. 13 schematically illustrates an example signal flow for allocatinguplink resources and providing uplink data in response to thatallocation;

FIG. 14 schematically illustrates an example signal flow for routinginformation and data in a relay network;

FIG. 15 schematically illustrates an example signal flow for a multi-hopacknowledgement (ACK) procedure;

FIGS. 16A to 16I schematically illustrate an example method ofestablishing a multi-hop uplink; and

FIG. 17 is a schematic flow diagram illustrating several of the stepsinvolved in communicating data asymmetrically on an uplink/downlink.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Referring first to FIGS. 4A and 4B, these provide a comparison between asymmetric uplink/downlink multi-hop signalling scenario and anasymmetric uplink/downlink signalling scenario. FIG. 4A illustrates asymmetric uplink/downlink case in which communications are multi-hoppedboth on a downlink 5 a from a base station la to a terminal device 4 avia intermediate devices 2 a and 3 a, and also on an uplink 6 a from theterminal device 4 a to the base station 1 a via the intermediate devices2 a and 3 a. FIG. 4B illustrates an asymmetric uplink/downlink case inwhich communications are direct on a downlink 5 b from a base station 1b to a terminal device 4 b, but are multi-hopped on an uplink 6 b fromthe terminal device 4 b to the base station 1 b via intermediate devices2 b and 3 b.

Referring now to FIGS. 5A and 5B, the impact of the asymmetricuplink/downlink scenario on the resource consumption and transmissiontime/medium time (time during which a radio link is in use conveyingsignalling and/or data) become clear. As discussed previously,multi-hopping permits lower power transmissions to be used, butincreases transmission time and medium time. FIG. 5A illustrates how themulti-hopping of both the control signal and the data signal (asconducted in FIG. 4A) take a relatively long time to be conveyed, due tothe processing delay on reception/retransmission at each intermediatestep in the route. In contrast, FIG. 5B shows how the transmissiontime/medium time is reduced in relation to the control signal sent fromthe base station (BS) to the terminal by transmitting the control signalin a single hop. While on the face of it this goes against the lowtransmission power goals of a mesh/relay type network, in reality thebase station will not be subject to the same transmission powerconstraints as the terminal device and relays within the network.Moreover, this arrangement is particularly advantageous for MTC devicesbecause of the relatively high volume of control signalling versus datasignalling which is typically utilised for this type of device.

Referring next to FIGS. 6A and 6B, a comparison of the symmetricuplink/downlink multi-hop signalling scenario and the asymmetricuplink/downlink signalling scenario when applied to a relay network isprovided. FIG. 6A illustrates a symmetric uplink/downlink case in whichcommunications are multi-hopped both on a downlink 10 a from a basestation 7 a to several terminal devices 9 a via relay nodes 8 a, andalso on an uplink 11 a from the terminal devices 9 a to the base station7 a via the relay nodes 8 a. FIG. 6B illustrates an asymmetricuplink/downlink case in which communications are direct on a downlink 10b from a base station 7 b to a terminal device 9 b, but are multi-hoppedon an uplink 11 b from the terminal device 9 b to the base station 7 bvia the relay nodes 8 b. It will be appreciated that the asymmetricuplink/downlink relay configuration of FIG. 6B will receive similarbenefits as the asymmetric uplink/downlink mesh network configuration ofFIG. 4B. In effect the intermediate devices of the mesh networkcorrespond to relays in terms of functionality. A typical differencebetween the two arrangements might be that the relay would not originatedata, may have a higher transmission power capability, and may be static(immobile) or semi-static (for example fixed in place on a train).

Certain embodiments of the present invention will now be described withreference to an implementation which uses a mobile communicationsnetwork operating in accordance with the 3GPP Long Term Evolution (LTE)standard. FIG. 7 is a schematic block diagram of a mobile communicationsnetwork and mobile communications devices forming a communication systemwhich operates in accordance with the 3GPP Long Term Evolution (LTE)standard. The mobile network includes a plurality of base stations knownin the art as enhanced Node-Bs 101 (eNBs) each of which includes atransceiver unit 103 enabling communication of data to and from aplurality of mobile communication devices 105 via a radio interface.Each mobile communication device 105 includes a transceiver forcommunicating data to and from the eNBs and a USIM which uniquelyidentifies the mobile communication device.

Each eNB 101 provides a coverage area (i.e. a cell) and communicatesdata to and from mobile communication devices 102 within the coveragearea/cell. Each eNB 101 is connected to a Serving Gateway (S-GW) 104which routes user data to and from the eNBs 101 and supports mobilitywhen mobile communication devices 105 handover between eNBs 101 as isknown in the art.

The mobile network is typically divided into a number of tracking areaseach of which comprise a number of eNBs. Together the tracking areasform a network coverage area providing access to the Public Land MobileNetwork (PLMN) over a geographic area. The S-GW 104 is connected to aPacket Data Network Gateway 106 (P-GW) which is the network entity fromwhich packet data is routed into and routed out of the network. Themobile telecommunication network also includes a Mobility ManagementEntity 107 (MME) connected to the S-GW 104 and the eNBs 101. The MME 107is responsible for authenticating mobile communication devices 105attempting to access the network by retrieving subscriber profileinformation stored in a Home Subscriber Server 108 (HSS). The MME 107also tracks the location of each mobile communication device 105 thathas joined the network. The eNBs grouped together form a radio networkpart of the PLMN and the infrastructure equipment of the PLMN, namelythe S-GW, MME and P-GW form a core network part of the PLMN.

FIG. 8 schematically illustrates an example downlink data and controlchannel structure for use in the LTE based network of FIG. 7. Accordingto the LTE standard, a physical down-link frame is used to communicatecontrol signalling and data on the downlink (base station to terminaldevice). FIG. 8 is a somewhat simplified form of this, for example a LTEframe usually includes 10 sub-frames but only 6 sub-frames 130 have beenrepresented for the downlink frame 120 of FIG. 8. Below therepresentation of the LTE frame 120 in FIG. 8 is an expanded version ofone of the sub-frames 130. In each sub-frame 130, a Physical DownlinkControl Channel (PDCCH) 140 is shown which occupies some time andfrequency resources within a resource zone that stretches across theentire frequency band (vertical) and across 1 to 3 symbols in the timeaxis (horizontal), where the time and frequency resources are usuallydistributed within that zone based on a random or pseudo-randomalgorithm. In contrast the Physical Down-link Shared CHannel (PDSCH) 150is comprised of a plurality of time and frequency resources which areallocated via the PDCCH. In effect, the PDCCH provides the mobilecommunications devices with the resource allocations and thecorresponding addressing information (for example the radio networktemporary identifier—RNTI). A mobile communications device cantherefore, based on the RNTI, know which resource allocations it shoulddecode to receive data intended for (addressed to) it. The data may beeither data for this mobile communications device only or for all mobilecommunications devices in the cell. In FIG. 8, two resource blocks 162,164 are highlighted. These could be allocated to a particular terminaldevice by control information provided in the PDCCH 140 in associationwith the RNTI of that particular terminal device. The terminal devicewould then know to decode data transmitted in that frequency/symbolallocation.

In similar fashion, FIG. 9 schematically illustrates an example uplinkdata and control channel structure for use in the network shown in FIG.7. As with the uplink-side, a physical up-link frame 220 is used tocommunicate control signalling and data on the uplink (terminal deviceto base station). Again, as with FIG. 8, FIG. 9 is a somewhat simplifiedform of this. In FIG. 9, the physical up-link frame 220 is divided intosub-frames 230. Below the representation of the LTE frame 220 in FIG. 9is an expanded version of one of the sub-frames 230. In each sub-frame230, a Physical Uplink Control Channel (PUCCH) 240 is shown whichoccupies some time and frequency resources within two resource zonesthat stretches across the entire time (symbol) band (horizontal) andacross a portion of the upper and lower extremities of the frequencyband (vertical). In contrast the Physical Up-link Shared CHannel (PUSCH)250 is comprised of a plurality of time and frequency resources whichare allocated via the PDCCH (in the downlink frame). The PDCCH thereforeprovides the mobile communications devices with the resource allocationsand the corresponding addressing information (for example the radionetwork temporary identifier—RNTI) for the transmitting as well asreceiving control signalling and data. A mobile communications devicecan therefore, based on the RNTI, know which resource allocations itshould transmit data on. In FIG. 9, two resource blocks 262, 264 arehighlighted. These could be allocated to a particular terminal device bycontrol information provided in the PDCCH 240 in association with theRNTI of that particular terminal device. The terminal device would thenknow to transmit data using that frequency/symbol allocation.

In a multi-hop network configuration, it is desirable to be able toselect the best route for communicating data. In some cases this may bethe route having the cleanest channel conditions (highest quality radiolink), and in other cases this may be the route having adequate channelconditions but a fewer number of hops. For example, data communicationsrequiring a greater degree of reliability may favour high qualitychannel conditions while data communications requiring a low latency(transmission delay) may prefer to limit the number of intermediatestages in the transmission. Furthermore, the quality of the radio linksmay have an impact on the time/frequency resources to be allocated to atransmission (for example, a number of resource blocks within thePUSCH), or the encoding type/rate and transmission power which should beused. In order to achieve this, the quality of each radio link ismeasured and reported back to the base station.

FIG. 10 schematically illustrates an example signal flow fortransmitting and receiving beacon signals, and allocating uplinkresources in dependence on the result. In FIG. 10, each of the basestation (eNB) and first and second relay nodes (RN1, RN2) transmitpredetermined beacon (reference) signals. The reference signal from eNBis received by the first relay node RN1, measured, and channel qualityinformation (CQI) is fed back to the eNB. The reference signal from thefirst relay node RN1 is received by the second relay node RN2, measured,and channel quality information (CQI) is fed back to the eNB via thefirst relay node RN1. Finally, the reference signal from the secondrelay node RN2 is received by the terminal device (UE), measured, andchannel quality information (CQI) is fed back to the eNB via the secondrelay node RN2 and the first relay node RN1. The channel qualityinformation may be transmitted to the base station as control signallingwithin the PUCCH. The channel quality information received at the basestation (eNB) is then used to allocate uplink grants for the respectiveradio links. As can be seen from FIG. 10, the respective uplink grantsare then transmitted (as control signalling in the PDCCH) directly tothe respective relay nodes and the terminal device. In this way, theuplink grants for each hop of the route can be tailored to complementthe channel conditions at each hop.

It will be appreciated that the same principles could be applied to amesh network, in which at least some terminal devices serve as relays inrelation to other terminal devices.

FIG. 11 schematically illustrates the use of the downlink control anddata channels to control the transmission of beacon signals from variousdevices on the network. In particular, control signalling providedwithin the PDCCH 340 of a sub-frame 330 indicates the radio resource(beacon transmission resource block) 360 within the PDSCH 350 at whichrespective beacon signals are to be transmitted. In this way the basestation is able to schedule beacon transmissions in such a way that thenetwork devices know when to transmit their beacon signals, andoptionally when to receive beacon signals from neighbouring devices.Based on the beacon signals, which have a predetermined transmit power,the receiving device is able to calculate a receive power of eachreceived beacon signal and communicate this back to the base station inthe form of an uplink control signal carried on the PUCCH.

Once the base station has decided on a suitable routing of uplink datafrom a terminal device, it transmits routing information to the terminaldevice and any intermediate devices on the decided route. The routinginformation may be broadcast by the base station using the PDCCH. FIG.12 schematically illustrates an example signal flow for transmittingrouting information and receiving uplink data along the nominated routein response. As can be seen from FIG. 12, three sets of routinginformation are transmitted, potentially in parallel, via the PDCCH tothe first relay node (RN1), the second relay node (RN2) and the terminaldevice (UE). No multi-hopping on the downlink is required. The first setof routing information (RN1->eNB) is directed to the first relay nodeRN1 and instructs the first relay node RN1 to direct communications tothe eNB. The second set of routing information (RN2->RN1) is directed tothe second relay node RN2 and instructs the second relay node RN2 todirect communications to the first relay node RN1. The third set ofrouting information (UE->RN2) is directed to the mobile terminal (UE)and instructs the mobile terminal to direct communications to the secondrelay node RN2.

Subsequently, when the mobile terminal transmits data to the basestation, it follows the instruction provided by the third set of routinginformation and directs the data to the second relay node RN2. Thesecond relay node RN2 then follows the instruction provided by thesecond set of routing information and directs the data to the firstrelay node RN1. The first relay node RN1 then follows the instructionprovided by the first set of routing information and directs the data tothe base station. In this way the base station is able to control therouting of uplink data through the network. The routing information mayutilise two addresses, that of the transmitter (so that the transmitteris aware that it is the intended recipient of the routing information),and of the receiver (so that the transmitter knows where to send thedata). Where the routing information is broadcast on the PDCCH, thereceiver address may also be useful to the receiver itself in knowing toexpect transmissions from the transmitter. The addresses may be radionetwork temporary identifiers (RNTIs), which serve to identify variousdevices (including base stations, relays and terminal devices) within anLTE network environment.

FIG. 13 schematically illustrates an example signal flow for setting andscheduling uplink grants in relation to the selected radio links andproviding uplink data in response to that allocation. The uplink grantsare broadcast to each of the first relay node RN1, the second relay nodeRN2 and the mobile terminal (UE) (and in fact any other devices withinrange) on the PDCCH, but are addressed individually to these devices. Nomulti-hopping on the downlink is required. In response, the terminaldevice (UE) transmits uplink data to the second relay node RN2 (asrequired by the third routing information in FIG. 12) using theallocated radio resources. On receipt, the second relay node RN2 relaysthe received data to the first relay node (as required by the secondrouting information in FIG. 12) using the allocated radio resources. Onreceipt, the first relay node RN1 relays the received data to the basestation (as required by the first routing information in FIG. 12) usingthe allocated radio resources. In this way, the base station is able toallocate radio resources on a per radio link basis. It will beappreciated that the signalling of FIGS. 12 and 13 could be combined,with the base station providing routing information and uplink grants ina single step.

FIG. 14 schematically illustrates an example signal flow for routinginformation and data in a relay network. FIG. 14 should be read inconjunction with FIG. 12. In FIG. 14, a base station (eNB) 410 isprovided. The base station 410 transmits routing information on thedownlink to each of a first relay node RN1 420, a second relay node RN2430 and a mobile terminal (UE) 440. These devices correspond to the basestation, first relay node, second relay node and base station discussedabove in relation to FIG. 12. In the present case, the base station 410is assumed to have previously determined the appropriate routing fromthe mobile terminal to the base station to be via the second relay node430 and the first relay node 420 in series. As can be seen from FIG. 14,the base station sets this route by transmitting routing information onthe downlink to each of the mobile terminal 440, the first relay node420 and the second relay node 430. On the uplink side, data istransmitted in a multi-hop manner from the mobile terminal 440 to thesecond relay node 430, from the second relay node 430 to the first relaynode 420 and from the first relay node 420 to the base station 410 inaccordance with the respective routing information.

FIG. 15 schematically illustrates an example signal flow for a multi-hopacknowledgement (ACK) procedure. FIG. 15 should be considered inconjunction with FIG. 14. When a transmitting device transmits data to areceiving device, it may expect an acknowledgment signal from thereceiving device indicating that the transmitted data has arrived. Ifthis acknowledgement signal is not received then the transmitting devicemay wish to resend the data (automatic repeat request—ARQ). A problemwith a multi-hop routing scenario is that a per-radio-linkacknowledgement cannot readily be enforced. In FIG. 15, when the mobileterminal (UE) transmits uplink data to the second relay node RN2, it canexpect the second relay node to reply with a per-link ACK. However, thisdoes not guarantee that the data will reach its final destination at thebase station. Subsequent hops in the route may then be entirelyinvisible to the mobile terminal, with further per-link ACKs beingtransmitted only to the device providing the uplink data at each stage.These further per-link ACKs serve a useful function in that if they arenot received a retransmission can be made from the first or second relaynodes for example. In order that the terminal device can know that thebase station has received the uplink data, the base station transmitstwo ACK messages. One of these is transmitted to the first relay node inorder that the first relay node is aware that the transmission of theuplink data has been successful. The first relay node can then dispensewith the uplink data as there will be no requirement for retransmission.The other ACK message is transmitted directly to the terminal device.The terminal device is therefore made aware that the uplink data hasreached its final destination at the base station, and can then dispensewith the uplink data. Until that time there is a risk, even if the ACKmessage from the second relay node RN2 has been received, that theuplink data could be lost further along on the route to the basestation. If the mobile terminal does not receive either the per-link ACKor the final ACK within respective specified time periods, it may decideto retransmit the uplink data.

In other words, in order to mitigate problems with automatic repeatrequests, the base station (eNB) sends two Acknowledge messages for onereceived data message; a per-link ACK towards transmitter (relay node)of this data message and a further ACK towards the source (end UE) ofthe data message.

It should also be noted that the base station may determine a delaybudget for uplink data transmission based on the number of intermediatedevices via which uplink data transmissions from the terminal device tothe base station are to be routed. The base station can use thedetermined delay budget to set a time-out period after which an uplinksignal transmitted from the terminal device to the base station can beassumed to be lost. This time-out period can be communicated to theterminal device in control signalling, and enables the terminal deviceto determine (for example) how long to wait for an ACK message beforeretransmitting uplink data.

FIGS. 16A to 16I schematically illustrate an example method ofestablishing a multi-hop uplink using beacon signals. One example methodof establishing an uplink multihop link is described in this sectionthrough a sample scenario, but it will be appreciated that other methodswill also be viable. This method is described in relation to a meshnetwork, but would also be applicable to a relay network, in whichcertain of the UE devices would be replaced with a dedicated relaydevice.

Referring first to FIG. 16A, a terminal device UE A 530 is connected inthe uplink to a base station eNB 510 via a terminal device UE B 520. Theterminal device UE B 520 is directly connected to the base station eNB510. The terminal device UE A 530 has a beacon transmission rangeindicated by the circle 535. A new terminal device UE C 540 enters inthe radio (beacon) range of UE A.

Referring next to FIG. 16B, the terminal device UE C 540, which wants toconnect to the network, will listen for at least a predefined beaconinterval, to hear if any terminal devices are nearby. Since the terminaldevice UE C 540 has entered the radio range 535 of the terminal deviceUE A 530, it will hear the beacon transmitted by the terminal device UEA 530.

If the terminal device UE C 540 hears more than one beacon it willmeasure the received power level of these to determine the strongestsignal and store the strongest transmitting terminal device, becausethis can be assumed to be the closest terminal device suitable toconnect to.

Referring next to FIG. 16C, once the terminal device UE C 540 receivesthe beacon sent from the terminal device UE A 530, it will send aconnection request back to the terminal device UE A 530. If the terminaldevice UE C 540 hears more than one beacon, it will send the connectionrequest to the terminal device that is assumed to be closest. Theterminal devices UE A 530 and B 540 will forward this request to thebase station eNB 510 where routing is managed.

Referring next to FIG. 16D, upon reception of this request, the basestation eNB 510 will send a connection grant message to directly to theterminal device UE C 540. The connection grant will instruct theterminal device UE C 540 to connect to the terminal device UE A 530,whenever it has something to send.

FIG. 16E assumes that another terminal device UE D 550, having a radiobeacon range 555, roams into range of the terminal device UE C 540.

In FIG. 16F, an assumption is made that all terminal devices are sendingbeacons at a certain interval. Eventually the terminal device UE C 540will hear the beacon sent from the terminal device UE D 550 and willnotice that the terminal device UE D 550 has entered its radio range.

Referring to FIG. 16G, upon reception of a beacon, the terminal deviceUE C 540 will report this fact and indicate the strength of the signalto the base station eNB 510, through the already established uplink.

Referring to FIG. 16H, after reception of the beacon report, the basestation eNB 510 will determine whether a change in the uplink route isnecessary. The decision may be made from the reported signal strengthbetween the mobile terminals or by the number of hops between the mobileterminal UE C 540 and the base station eNB 510.

Referring to FIG. 16I, because the number of hops for the current routebetween the base station eNB 510 to the terminal device UE C 540 is 3hops, and through the terminal device UE D 550 is 2 hops, the basestation eNB 510 instructs the terminal device UE C 540 to reroute toconnect with the terminal device UE D 550 to reduce the number of hops.Reducing the number of hops is beneficial to lower latency and overhead.

By operating through the method described with reference to FIGS. 16A to16I, routing can be fully managed by the base station, enablingreduction of complexity at the mobile terminal.

FIG. 17 is a schematic flow diagram illustrating several of the stepsinvolved in communicating data asymmetrically on an uplink/downlink. Inparticular, at a step S1, a terminal device establishes a connection tothe network. This could be achieved using the method described inrelation to FIGS. 16A to 16D for example. Then, at a step S2, channelquality information, relating to the radio links available betweendevices within the network, is obtained and communicated to the basestation. This could be achieved using the method described in relationto FIGS. 16E to 16G for example. At a step S3, the base station setsscheduling information (for example routing information and uplinkgrant) based on the received channel quality information. This could beachieved using the method described in relation to FIG. 16H for example.At a step S4, the base station transmits the scheduling informationdirectly to the network devices. This could be achieved using the methoddescribed in relation to FIGS. 12 to 14, 16G and 16I for example. At astep S5, uplink data is transmitted in a multi-hop manner to the basestation in accordance with the scheduling information. This could beachieved using the method described in relation to FIGS. 12 to 14 forexample. At a step S6, a two-part acknowledgement (ACK) procedure isconducted to inform the terminal device that the uplink data has beensuccessfully received at the base station. This could be achieved usingthe method described in relation to FIG. 15 for example. Finally, thecommunication is completed at a step S7.

1-35. (canceled) 36: A terminal device for wirelessly communicating datato and from a base station via one or more of a plurality ofintermediate devices within a wireless communications system, theterminal device comprising: reception circuitry configured to wirelesslyreceive, directly from the base station, downlink signals includingterminal control signals that identify a target device to which theterminal device is to direct uplink signals intended for the basestation, the target device being one of the intermediate devices; andtransmission circuitry configured to wirelessly transmit the uplinksignals to the target device for subsequent transmission to the basestation. 37: The terminal device according to claim 36, wherein theterminal control signals comprise scheduling information having aplurality of address fields, each of the address fields comprising atransmitter address field identifying the terminal device and a receiveraddress field identifying the target device. 38: The terminal deviceaccording to claim 37, wherein the address fields are radio networktemporary identifiers (RNTIs) specified on a physical downlink controlchannel (PDCCH) broadcast by the base station. 39: The terminal deviceaccording to claim 38, wherein the control signals comprise schedulinginformation specifying one or more of a transmission power, data rate,transmission frequency, transmission timeslot and number of resourceblocks for the uplink signals. 40: The terminal device according toclaim 36, wherein the terminal device serves as an intermediate devicein relation to uplink communications from another terminal device to thebase station. 41: A method of wirelessly communicating data between aterminal device and a base station via one or more of a plurality ofintermediate devices within a wireless communications system, the methodcomprising: wirelessly receiving downlink signals from the base station,by reception circuitry of the terminal device, the downlink signalsincluding terminal control signals that identify a target device towhich the terminal device is to direct uplink signals intended for thebase station, the target device being one of the intermediate devices;and wirelessly transmitting the uplink signals to the target device, bytransmission circuitry of the terminal device, for subsequenttransmission to the base station. 42: The terminal device according toclaim 36, wherein the uplink signals and the downlink signals aremachine type communication (MTC). 43: The terminal device according toclaim 36, wherein the target device receives the uplink signals from theterminal device and transmits the uplink signals to a secondintermediate device for subsequent transmission to the base station. 44:The method according to claim 41, wherein the terminal control signalscomprise scheduling information having a plurality of address fields,each of the address fields comprising a transmitter address fieldidentifying the terminal device and a receiver address field identifyingthe target device. 45: The method according to claim 44, wherein theaddress fields are radio network temporary identifiers (RNTIs) specifiedon a physical downlink control channel (PDCCH) broadcast by the basestation. 46: The method according to claim 45, wherein the controlsignals comprise scheduling information specifying one or more of atransmission power, data rate, transmission frequency, transmissiontimeslot and number of resource blocks for the uplink signals. 47: Themethod according to claim 41, wherein the uplink signals and thedownlink signals are machine type communication (MTC). 48: The methodaccording to claim 41, wherein the target device receives the uplinksignals from the terminal device and transmits the uplink signals to asecond intermediate device for subsequent transmission to the basestation. 49: The method according to claim 41, further comprising:receiving, by the reception circuitry of the terminal device, seconduplink communication from another terminal device; and transmitting, bythe transmission circuitry of the terminal device, the second uplinkcommunication to the base station. 50: The terminal device according toclaim 36, wherein each intermediate device of the plurality ofintermediate devices is as relay node, and the target device is a targetrelay node. 51: The method according to claim 41, wherein eachintermediate device of the plurality of intermediate devices is as relaynode, and the target device is a target relay node. 52: The terminaldevice according to claim 36, wherein the reception circuitry isconfigured to receive an acknowledgement message from the target device,the acknowledgement message indicating that the uplink data issuccessfully received by the target device. 53: The terminal deviceaccording to claim 52, wherein the reception circuitry is configured toreceive a second acknowledgement message from the base station, thesecond acknowledgement message indicating that the uplink data issuccessfully received by the base station. 54: The method according toclaim 41, further comprising receiving an acknowledgement message fromthe target device, the acknowledgement message indicating that theuplink data is successfully received by the target device. 55: Themethod according to claim 54, further comprising receiving a secondacknowledgement message from the base station, the secondacknowledgement message indicating that the uplink data is successfullyreceived by the base station.